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(3) Essays Towards a Theory of Knowledge. By A. Philip. Pp. 126. (London: G. Routledge and Sons, Ltd., 1915.) Price 2s. 6d. net.



HE term Kultur is the equivalent of our "civilisation"; Kulturgeschichte is "history of civilisation." In a secondary sense the German term is narrowed to mean "the organisation of a people's life in which the ideals of religion, morality, and science come to realisation." The popular present-day use of the term, therefore, actually coincides with our "culture, "civilisation viewed on its higher side." It is only Chauvinist writers who have reduced it, at a very ill-chosen time, to the connotation of morality.

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The popularly written essays, which Prof. Paterson has brought together, on Germany's contribution to the world's culture have the merit of impartiality. It is a mistake to suppose, by way of a reaction from Germany's pretensions to pre-eminence, that her work is second-rate and second-hand, however industrious.

In philosophy Mr. Lindsay observes that the German genius is supreme in the production of metaphysical systems. Such work suits the German mind, which has produced both "the dryas-dust and the romantic fairy-tale." "The first question a German asks about a philosopher is'What is his Weltanschauung?'"-his "worldvision." Could we talk about the world-vision of Locke or Hume? Mr. Lindsay is probably right in regarding German philosophy as "the most characteristic contribution which Germany has made to the common treasure of the human spirit." A typical feature of it is the passion for monism, Kant alone being an exception.

The best and most detailed essay in this book is that on science by Prof. J. Arthur Thomson. "It is probable that the Germans in their normal condition have the most orderly minds in Europe," but they have made far-reaching discoveries as well. Prof. Thomson sketches fully the course of investigation in biology, physics, and chemistry during the last hundred years, and places the German contributions in the order of their appearance, so that the reader may estimate their importance and compare them with those of other peoples. In biology the cell-theory, which "must be placed beside the evolution theory as one of the foundation-stones of modern biology," was almost entirely the work of Germans. interesting episode of chemistry is this:


"Sixty years ago an obscure German chemist obtained an oily liquid from coal-tar oil, which gave a beautiful tint with calcium chloride; five years later, another separated a similar liquid from a derivation of coal-tar oil."

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"the probable fallacy of using the history of science as an index of national or racial qualities," but he notes that "the reading public for concrete science is enormously greater in Germany than in Britain, and that there is a stronger faith (which we believe to be warranted) in what science can do for the amelioration of human life."

In Prof. Sadler's account of education two points may be marked :—

"England hesitated between two opposing theories, the theory of State control and the theory of group autonomy under the general supervision of the State. Germany came to a decisive conclusion on this fundamental question of procedure. Great Britain (and particularly England) remained divided in conviction about it, and therefore irresolute in policy. Germany standardised her education upon a system. Britain, distrustful of State control, compromised.'

Not only English, but German observers have often remarked that the intellectual apprehension of the average educated German is ten times quicker than that of the average educated Englishman. But the intellectual judgment of the average educated German is most uncertain and weak, and often most conventional. The German will form ten foolish inductions to the Englishman's one. This corresponds to a real difference in temperament, between the cool, phlegmatic Briton and the emotional German. One result of this emotionalism seems to be the extraordinary solidarity of both German culture and German national feeling; yet British solidarity is as real, though longer-circuited.

(2) After the results of understanding, the principles of it, and the principles of the reality which we try to understand. Mr. Sturt writes from the point of view of personal idealism, and treats logic dynamically. His main text is the creative, inventional power of understanding. sight of understanding he advances as the strongest argument against epiphenomenalism, such as that of Shadworth Hodgson, according to which

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But he does not explain consciousness. sciousness, again, is characterised by passion; by neglecting this fact and the fact that it is "totalworking," intellectualism "has obscured the true. nature of intelligence."

On the fundamental nature of consciousness, creative and passion-wrought, Mr. Sturt has a big assumption, already made by McDougall, viz., "a true logic is impossible without animism.' He has some interesting observations and phrases:

"Felicitous naming, felicitous phrasing add enormously to the power of thought," especially, we may add, when thought is being thought about. Thus, the soul is not weak and shadowy, a slender breath, animula vagula blandula, nor a mere point; "a human soul is very large"; it has a wealth of faculties "correspondent to the richness of the world."

If the soul is a big thing, then the mental sciences, including logic, are bigger than the writers of the past would lead us to suppose. But Prof. Stout has said, "to the psychologist the conception of a soul is not helpful." Further, there is a social soul; a society of a hundred individuals is more than a hundred souls. On the "generation" of souls he says:

"There must be some source of soul-life . we cannot say that we are not surrounded by a soul-element, and that the whole universe is not pervaded by soul-life whence individual souls come into being as they are wanted."

This is precisely the doctrine of the Dayaks and other savages of the East Indies.


(3) "Dynamic" is nowadays a blessed word. It assists Mr. Philip towards a theory of knowledge. In this, the ultimate reality is "potential energy." "Sensation is obstructed action"; "sensations only mark the interruptions in the dynamic activity in which we as potent beings partake." But these obstructions do not constitute essence of our experience, they merely denote it. For this essence we must look to our activity as such. Space is the absence of physical obstruction. Time is the periodicity of natural force. Mr. Philip has some useful inferences drawn from the experiences of the blind, recently recorded by M. Pierre Villez. Particularly significant is his insistence throughout the book (which contains four short essays) on the necessity for metaphysics to found upon physics, a necessity hitherto almost totally ignored.



Canadian Institute: General Index to Publications, 1852-1912. Compiled and edited by J. Patterson (Hon. Secretary). Pp. 518. (Toronto: University Press, 1914.) Price 5.00 dollars. THE pioneers of a new country are mainly preoccupied in developing its material resources, but there is always a remnant faithful to the intellectual life. Cut off from the companionship of their peers, these men gather themselves into local societies, and adopt the common form of regular meetings for the reading of papers.

Some two score such societies were scattered through the Dominion when, in 1882, the Marquis of Lorne founded the Royal Society of Canada. The older societies were not superseded, but affiliated, and they report annually by delegates on their work for the year. The most important Montreal (founded 1827) and the Canadian Inof them were the Natural History Society of stitute of Toronto (1852). It is this latter body which now issues, in a handsome volume of 518 double-column pages, an index to its 35 volumes of publications from 1852-1912.

The index has been prepared with much care and labour, the most important papers being indexed almost by paragraphs, and as it is arranged like a dictionary, alphabetically, it ought to be easy to find anything to which there is the slightest clue.

The pity of all such series is that they become the burial-ground of much that is valuable beneath heaps of rubbish. There are hundreds of references here to "papers" (especially in the early volumes) which are merely translations of some passage from the classics, fugitive reviews of forgotten books, scraps of antiquarian lore from anywhere on earth except Canada. But the real core of value is to be found in the original contributions on the history, customs, and folklore of the rapidly vanishing Indian tribes; the early history and settlement of Canada; its geology, minerals, botany, flora and fauna, with their consequent biological problems. Even in physics, though most that is worth while finds its way to European publications, there are observations special to Canada (e.g., peculiar ice-formations) labours of her own pioneers of science. guished names like those of Sir Daniel Wilson, Sir J. W. Dawson, and Goldwin Smith are a guarantee that there is much in these Proceedings which ought not to be smothered. index will enable any student, in spite of the dust, to rescue whatever concerns his own line of study. Towards Racial Health. By Norah H. March. With a Foreword by Prof. J. A. Thomson. Pp. ix+326. (London: G. Routledge and Sons, Ltd., 1915.) Price 3s. 6d. net.

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IN this little book Miss March deals with one of the most serious difficulties which lies in the path of those engaged in training the young. Children are taught elementary rules of health in relation to food, drink, and exercise, but sex is seldom

mentioned. The majority of young people are left to find things out for themselves, or from their equally blind or ignorant fellows. The danger of this method, especially in the early days after puberty, when bad habits formed are so difficult to eradicate subsequently, is recognised by educationists, but, as a rule, nothing is done to counteract the evil. Miss March shows that instruction on this most important matter can be given without any loss of delicacy, by making biology a school subject, and by practically studying the development of certain plants and animals. She also very rightly urges that there should be greater frankness and confidence between parents and their children, and that reticence on the part of either should be discouraged. Great pains have been taken to make the biological statements clear and accurate.

The book is addressed to parents and teachers, not to the children themselves. There are many subjects dealt with, such as prostitution and sexual diseases, which it is quite unnecessary for mere children to understand; the evils of the world will become apparent quite soon enough, and we feel sure that these evils would be less if only young men and maidens were, at an early stage, taught to understand and respect their own bodies. It is because Miss March has made a successful attempt to induce parents to realise their responsibilities that we welcome her book.

W. D. H.

The Theory of Measurements. By Dr. A. de Forest Palmer. Pp. xi + 248. (New York: McGraw-Hill Book Co.; London: Hill Publishing Co., Ltd., 1912.) Price 2.50 dollars or IOS. 6d. net.

THE author has prepared this treatise on the theory of measurements to meet the needs of students in engineering and advanced physics, and to impress on them the importance of realising the significance and the precision of the measurements made.

In the first seven chapters the general principles of measurement, the nature and distribution of errors, and the methods which are employed to arrive at the most probable result, are set forth clearly.

Measurements of various kinds are discussed, to show the importance of determining the precision of the result obtained if the operation is to be of any real value.

A general discussion of errors, which is very clearly stated, leads up to the method of least squares, and throughout the subject numerical examples are worked out so that the student may see for himself the treatment of measurements and the errors which arise.

The second half of the book is devoted to a general discussion of the precision of measurements, to which the earlier chapters have formed a suitable introduction. It is in this portion that the author's aim to lead the student to test systematically the results which he obtains is best seen, and the guidance given for the ade

quate discussion of completed observations and of proposed measurements is most valuable.

The whole subject is clearly and comprehensively set forth, and is illustrated by numerous examples of physical measurements, which are fully worked out. The book is to be recommended to the student as a useful guide to the systematic discussion of measurements and the determination of their adequacy. M.

LETTERS TO THE EDITOR. [The Editor does not hold himself responsible for Neither opinions expressed by his correspondents. can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]

Supposed Horn-Sheaths of an Okapi.

ARRIVING in London after an absence of more than three years in the Belgian Congo I have been considerably surprised at what appears to have been a mistake on the part of Messrs. Gerrard, the taxidermists, in connection with the skin and skeleton of an okapi, one of a series obtained recently by me in the Ituri forest.

The okapi in question was sent to the director of the Tervueren Museum in Brussels, and afterwards forwarded by him to Messrs. Gerrard in London; the skin in one case, the skeleton in another. In the box containing the skeleton I had originally packed a number of other bones, including the skull of a very young waterbuck. These bones and the waterbuck skull were taken out in Brussels and retained for the museum according to agreement. Unfortunately, the detached horns of the young waterbuck seem to have been overlooked, and when found by Messrs. Gerrard it was assumed that they belonged to the okapi, with which, of course, they had nothing whatever to do. It would appear, moreover, from a letter in the columns of NATURE of July 9, 1914 (vol. xciii., p. 479), that the late Mr. Lydekker supported Messrs. Gerrard in this belief.

If it is a fact that these two horn-sheaths were labelled as belonging to the okapi I can only say that this was not done by me or any of my servants in the Ituri, none of whom could speak or write anything but Kiswahili, and if any label had been attached in Brussels no doubt it would have been written in French. Nothing is mentioned in my register of specimens about horny-sheaths. On the contrary, I distinctly say, "Horns 1 in., skincovered."


The extraordinary statement that the giraffe-like horns of an okapi, an animal far removed from the antelopes, could in any circumstances have hornysheaths resembling those of the prongbuck, naturally aroused the interest of Sir E. Ray Lankester, whose knowledge of the anatomy of the okapi is unequalled. am considerably indebted to him for going into the matter without waiting for my return, and dispelling the illusion. His view of what had probably happened, as stated in his letter to NATURE (March 18, 1915), is perfectly correct, except as regards the "well-intentioned servant."

The whole of my series of seven okapi skins has now safely reached England, I am glad to say, having been, through the kindness of the Belgian Minister, sent direct to London from the West Coast, together with two skeletons and various soft parts preserved in spirit.

Altogether more than eighteen months were spent in

the Ituri forest hunting this scarce and extraordinary animal, and searching for the hypothetical Elephas pumilio (Elephant nairn "), accompanied each day by one of my friends, the little Bambuti pigmies, without whose co-operation and assistance I could have done very little indeed. Elephants were everywhere, but not a sign of any pigmy species could I discover in the Ituri.

On several occasions I saw the okapi alive, sometimes at very close quarters, but so ghost-like, wary, and elusive is it, so difficult to track, even for the little "animal men," and so difficult is it to see in the prevailing gloom, that I only succeeded in shooting two. A third one (No. 531) of the series was shot by Commandant Hedmark, an officer in the Congo service, who spent three days shooting with me at one of my forest camps, and came upon the animal quite by accident.

A fourth (No. 717) was killed, late one afternoon, in mistake for a buffalo, by Mr. A. E. H. Reid, a prospector, also in the Congo service, and given to me. This specimen is of considerable interest, being an old male with well-developed horns some 4 in. in length, and skin-covered except at the tip, where, instead of a tuft of hair, the bony horn-core is bare, somewhat cup-like in shape, and of modified, white, polished, very hard, compact bone. The remaining three skins were procured from natives and are very incomplete.

Hitherto there has been considerable confusion as to the sex to which the comparatively few skulls handled by naturalists belonged, and mainly for this reason there has been a doubt as to whether both sexes or only the male develops horns. There is no question as to the sex of four of my specimens, three males and one female. Two of the males have horns, but the third, being very immature, has not yet developed them. The big female, although an old animal, as shown by the condition of the teeth, has no horns or any signs of developing ossicones. This being so, I think I am justified in saying that my specimens go far towards proving that only the male okapi carries horns.

They also help to prove that the female okapi, unlike most other animals, attains a greater height and bulk than the male, a peculiarity suspected by a writer in Country Life (October 25, 1913) as the result of measurements of mounted specimens.

Giraffe-like as the animal seems, and is, it is only when extremely young that the backward slope of the back is very noticeable. It does not feed on any species of water-plant so far as I know. In fact, it seldom frequents low situations near the water. Its food consists of leaves of the undergrowth and young saplings, and in feeding it reaches to a considerable height, pulling down leafy twigs with its long prehensile tongue. It does not, I think, feed at night, but in the early evenings and the mornings until at least as late as nine or ten o'clock. It is not a jungleloving animal at all, but prefers the higher and drier parts of the forest, where the trees are big and the undergrowth comparatively scanty. It has no skulking bongo-like habits, but is never seen in the open. When going away at speed its neck is held straight in front, and it will jump obstacles rather than go beneath them, like the bongo and the little red buffalo.

Everything points to the okapi being the progenitor of the giraffe, or at least there seems little doubt that both are from the same stock. The okapi certainly does not appear to me to have any affinities with the antelopes. CUTHBERT CHRISTY.

Royal Societies Club, St. James's Street, S.W.,
May 24.

A Further Extension of the Spectrum.

IN NATURE of May 7, 1914 (vol. xciii., p. 241), I stated that I had extended the ultra-violet limit of the spectrum to the neighbourhood of wave-length 900 Angström units.

I have now succeeded in carrying my observations to wave-length 600. This result is chiefly due to the use of helium of considerable purity in my spectroscope and discharge tube. The apparatus is the same grating vacuum instrument which I have employed for several years, but perfected in such a way as to make it much more nearly air-tight than ever before. The spectrum which is obtained with a disruptive discharge in helium contains, between wavelength 1250 and 600, upwards of fifteen lines, some of them of some strength.

My work with hydrogen confirms the existence of the series predicted by Ritz with members at 1216, 1026, and 972. But, owing to the great difficulty of obtaining the gas content of my spectroscope absolutely free from impurities, I am not even yet able to identify positively the source of certain strong lines which occupy the positions demanded by the analogue of the Pickering series, and Occur both when hydrogen and when helium are employed. THEODORE LYMAN. The Jefferson Laboratory, Harvard University, May 11.

The Distribution of the Electrons in Atoms. THE spectra which are obtained by the diffraction of X-rays by crystals are characteristic both of the substance which emits the X-rays and of the crystal which acts as the grating. If the lines of an accurately ruled plane grating are small in width compared with their distance apart, the intensities of the different orders of spectra are nearly the same. If, however, the lines have a width comparable with the grating constant, the intensities of the higher orders rapidly diminish. When a crystal diffracts a beam of X-rays, the different layers of atoms correspond to the lines of the ordinary transmission grating, so that the relative intensity of the higher orders of spectra will depend upon the ratio of the effective diameter of the atoms in scattering the X-rays to the distance between the successive layers of atoms.

There are good reasons for believing that it is the electrons in atoms which scatter the X-rays. On this assumption it may be shown that if the density of the space distribution of the electrons in each layer of atoms is some function f() of , where the z axis is taken normal to the reflecting planes, the ratio of the amplitude of the nth order spectrum to the amplitude it would have if all the electrons were in the same plane is :

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where bad is the grating space, and ẞ is the phase angle of the reflected ray. If it is possible to find some function f(z) which will lead to the values of P/P, as determined experimentally, an indication will be obtained of the distribution of the electrons in the atoms.

W. H. Bragg has published experimental results (Phil. Mag., vol. xxvii., p. 895, 1914) showing the rate of variation of the intensity with the order when X-rays are reflected from rock-salt. It can be shown from his data that the intensities of the different

orders cannot be accounted for by assuming that the atoms in the salt crystal are made up of single rings of electrons, or by assuming a uniform volume distribution of the electrons in spheres. A distribution which fits Bragg's data acceptably is an arrangement of the electrons in equally-spaced, concentric rings, each ring having the same number of electrons, and the diameter of the outer ring being about 0-7 of the distance between the successive planes of atoms.

If, as D. L. Webster assumes (Phys. Rev., vol. v., p. 238, 1915) the trains of waves of the primary beam of X-rays are short compared with the distance which the rays penetrate the crystal, certain corrections have to be applied to the experimental data, and on this assumption it can be shown that the average distance of the electrons from the centre of the atom is small compared with the distance between the atoms.


Experiments are now in progress to test the validity of Webster's assumption and to determine accurately the rate of variation of the intensity of the reflected beam with the order. It is hoped that it will be possible in this manner to obtain more definite information concerning the distribution of the electrons in the atoms. ARTHUR H. COMPTON.

Palmer Physical Laboratory, Princeton, N.J.,

Apri! 29.

I HAVE to thank the Editor for his kindness in allowing me to see Mr. Compton's letter. I believe Mr. Compton is right in ascribing the rapid decline in the intensities of the X-ray spectra as we proceed to higher orders to the fact that the atom should not be treated as a point, but as a distribution of electrons in space; if this is so, we may hope to determine this distribution when we have measured the relative intensities accurately and have learnt to interpret them. This hypothesis and its consequences were discussed by me in the Bakerian lecture given before the Royal Society in March last. As only short notices of the lecture have yet appeared in print, I may mention one or two of the points then raised.

It seems convenient to imagine a periodic distribution of density such as occurs in a crystal to be analysed by Fourier's series, in a manner suggested by previous work of Rayleigh, Schuster, or A. B. Porter (Phil. Mag., January, 1906, p. 154). Each harmonic distribution of density is responsible for one order of reflection. The results of measurements with calcite seem to show that the intensity (not the ampli tude) of the reflection by a "harmonic reflector" is proportional to the amplitude of the harmonic distribution of density; that is to say, that the intensity of the reflection is proportional to the mass of the reflector. It is necessary to explain, not only why the intensities of the various orders fall off approximately as the inverse square of the number of the order, but also why atom-bearing planes give intensities whose reflections are proportional to the squares of the distances separating the planes. It appears that both laws follow from the same hypothesis, viz. that which supposes the reflecting electrons to be distributed in space through the volume of the atom, and which imagines much overlapping to take placeatoms of one plane being thrust far into the interstices of the next.

Experiment seems to fit in with these ideas. Probably, however, it is necessary to take account also of a difference in the distribution in different atoms. For example, certain results seem to indicate that the sulphur atom is more concentrated than the zinc. The University, Leeds. W. H. BRAGG.

Early Figures of the Remora.

As remarked by Dr. Albert Günther, in his article on the history of the Remora ("On the History of the Echeneis," Ann. Mag. Nat. Hist., 1860, ser. 3, vol v., p. 386), "there is scarcely a fish of the existence of which the ancients have been equally certain, and which has so much occupied their imagination as the Echeneis of the Greeks or Remora of the Latins." Also, the same author continues, "there is scarcely a group of fishes . . . which has been so little comparatively treated, and which has experienced a similar splitting up into nominal species."

The ancient legends associated with this fish, from which it derives its name, signifying "ship-holder," persisted until well into modern times; and what is probably the earliest illustration of the Remora in printed books shows several of these creatures engaged in arresting the progress of a vessel. The curious woodcut referred to is found in that late fifteenthcentury work known as "Hortus Sanitatis," the author or compiler of which styles himself Johannes von Cube, or Cuba, by some thought to have been a punning pseudonym for Dr. Wonnecken, town

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physician of Frankfort. First printed about 1490, the work enjoyed considerable popularity, as is proved by its having passed through several editions. A copy of the design representing the Remora, taken from the 1536 edition, is shown in Fig. 1.

The next oldest illustration of the Remora appeared in a book, or perhaps a map, printed during the first half of the sixteenth century, and was copied by Conrad Gesner in book iv. of his "Historiæ Animalium," published in 1558. It is shown in Fig 2. The same figure, more or less modified, reappears in various seventeenth-century works on natural history, as, for example, those of Nieremberg, Aldrovandi, Jonston, Ruysch, and others.

Search for the original after which Gesner's figure was copied has proved unavailing; but the subject of the sketch, and also the verbal description, are traceable to the account of a West Indian species of sucking-fish, the first printed description of which is found in the "Libretto" of Peter Martyr of Anghera, published in 1504, and reprinted three years later in the collection of voyages known as "Paesi novamente Trovati."

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